1. Field of the Invention
This invention relates to the field of biochemical instrumentation. More particularly, the invention relates to DNA synthesis. By way of further characterization, but not by way of limitation thereto, the invention is a disposable DNA synthesis column which includes a transparent tube for viewing of the resin beads within the tube. The column is secured into and removed from a housing by means of a screw threadably engaged with the housing.
2. Description of the Related Art
Separations performed by liquid chromatography have employed separation columns for a number of years. In general, these columns are expensive to purchase and time consuming to install and remove. The separation material in those columns is re-used and the columns may be utilized for a year or more without being replaced. The separation material in the column is washed after each use by eluting a wash solution through the column. DNA synthesis, on the other hand, requires that the resin beads in the column be removed after the synthesis in order to obtain the synthesized DNA present on the resin beads. Because the column must be removed after each separation, the difficulty in removing and installing columns is a very important consideration in DNA synthesis. In addition, while the columns must be removable, they also must be tightly sealed to prevent contamination and to prevent leakage of the eluent from a column.
In the past, the removable and disposable portions of the DNA synthesis columns were complicated to separate. That is, a number of O-rings, collars and threadable assemblies with nuts and fittings were employed which made the column expensive and complicated and thus difficult to take apart. The portion of the column which was replaced was the tube portion with the packing material or resin beads. The rest of the fittings were re-used. Many of these columns, because of the difficulty in fitting a large number of parts together, incorporate a dead volume area within the column. That is, there are unintended spaces in the column into which the liquid would be trapped. Because of the dead volume, errors in the synthesis could occur if a portion of a first liquid chemical remained in the dead volume while the next liquid in the series was flowing through. That is, if the first liquid filled the dead volume and then gradually was replaced during elution of the second liquid, then this first liquid would be mixed with the second liquid and could result in the wrong sequence on the DNA chain.
Previously employed columns have been made of opaque material. That is, because of the seals required and because of the amount of handling which must be done to the column during replacement of the tube, the columns had to be made of a relatively durable material. In those situations where the tube was made of a transparent material such as glass or plastic, the tube was relatively difficult to fabricate since flanges and the like were required to seat against O-rings or the like to provide a liquid seal. Thus, metal tubes were preferred. It is desirable in DNA synthesis to view the synthesis itself and thus, columns employing a transparent tube would be desirable.